In general such a switch is intended for coupling one end, eg. the front end of a light guide which is hereinafter referred to as a "common" light guide, with an optical component which is selectable from a plurality of such components, hereinafter referred to as "particular" components. To facilitate the description, it will be supposed that the switch is used more particularly to direct light coming from the common guide and going towards a particular component. However, it must be understood that by virtue of the fact that light can travel in either direction along a given path, a switch which directs light towards a particular component is just as capable of injecting light from the particular component into the said guide.
The above-mentioned particular components may be constituted by detectors for example, but in fact they tend more often to be constituted by systems for injecting light into "particular" optical fibers. Similarly, the common guide is most often constituted by a "common" optical fiber.
In known manner such a switch includes:
collimator means for transforming a highly divergent beam leaving the front end of the common guide into a substantially parallel external beam of increased cross section; and
controllable deflector means for deflecting said substantially parallel beam to direct it towards a selected particular component.
Naturally, said "collimator" means becomes "focusing" or "light injecting" means if the light is considered to be travelling towards the common guide.
One such known switch is described in U.S. Pat. No. 4,304,460 (Tanaka et al., assignors to Matsushita).
This known switch includes collimator means constituted by a lens and deflector means constituted by a rotatable mirror.
Such a switch may, for example, enable a user to select a program of interest from a plurality of television programs transmitted to the user over a plurality of optical fibers.
Given the very small transverse dimensions of the optical fibers used, this known switch is either extremely bulky in comparison with the fibers, or else it is very difficult to manufacture if light losses are to be kept as low as possible. In particular, the position of the rotatable mirror must be accurately defined both with respect to the collimator lens and with respect to said particular components.
Preferred embodiments of the present invention provide a light guide circuit switch which is simpler to manufacture and which causes little loss of light.